基于电催化析氧反应的硫化物催化剂研究进展

氢能作为一种可燃烧的新型能源,凭借其清洁无污染等优点,被认为是人类从根本上解决能源与环境等全球性问题的理想替代能源.电解水是生产高纯度氢气的重要方法之一,也是现代清洁能源技术的重要组成部分.随着实际需求的不断增长,如何利用高效低耗的电催化剂来提升反应速率,已经成为当前新能源领域的研究重点之一.电解水反应由阴极析氢反应(HER)和阳极析氧反应(OER)两个半反应组成,其中HER反应相对容易进行;而相比于HER反应,OER反应动力学缓慢,是影响电解水效率的主要原因.为了提高电解水制氢的能量转化效率,高效OER电催化剂成为研究电解水制氢技术的关键因素.过渡金属催化剂由于其特殊的d轨道结构和在地球上丰富的储备量成为OER催化剂研究领域的热点,但是目前存在的主要问题是,与贵金属催化剂相比,过渡金属催化剂的催化活性较差.因此,发展一些高催化活性和高效稳定的电催化剂,成为该领域研究关注的重点.在过去的十余年间,硫化物、硒化物、磷化物和硼化物等非贵金属基OER电催化剂被大量研究并取得了长足的发展.在这些催化剂中,硫化物型电催化剂不仅具有成本优势,而且在析氧过电位、耐久性等方面正在接近甚至超越RuO2和IrO2等贵金属催化剂,颇具应用潜力.本文主要介绍了电解水析氧反应在不同电解质中的反应机理,从硫化物型OER电催化剂的物理化学性质入手,证实了硫化物型OER电催化剂在析氧反应中具有独特的优势,最后综述了有关硫化物型OER电催化剂在改进策略等方面的研究进展.     

MnNiCoCrFe多孔高熵合金的电催化析氧性能

用化学腐蚀方法制备出3D多孔自支撑型Mn₅₀Fe_12.5Co_12.5Ni_12.5Cr_12.5高熵合金。电化学测试结果表明,将这种高熵合金放入1 mol/L KOH的碱性溶液中,电流密度为10 mA·cm^-2时过电位为281 mV,Tafel斜率为63 mV/dec,表明其电催化性能优于商业RuO₂的性能。在电流密度为50 mA·cm^-2的条件下连续工作50 h,工作电压没有明显的升高,表明这种富锰高熵电催化电极材料具有优异的析氧稳定性。电化学阻抗谱表明,这种自支撑型结构的块体高熵合金催化剂具有出色的导电性,与负载型催化剂相比其电子转移能力显著提高。     

自支撑NiMoP@NiFeP异质结电极的制备及其电催化析氧性能研究

析氧反应(OER)是水分解一个重要的半反应,开发高效稳定的非贵金属基电催化剂用于大规模产氢仍面临巨大挑战。采用水热和低温磷化的方法在泡沫镍(NF)上原位构筑了NiMoP@NiFeP/NF复合电极。利用扫描电子显微镜(SEM),X射线光电子能谱(XPS)等对所制备电极的微观形貌和组成电极元素的价态进行表征。此外,通过电化学测试表明,NiMoP@NiFeP/NF电催化剂在1 mol/L KOH电解液中驱动100 mA/cm²的电流密度仅需246 mV的过电势,塔菲尔斜率为54.6 mV/dec,且至少能保持20 h的稳定性。为制备非贵金属基的催化剂,用于能源的存储和转换提供了一种有效途径。     

凹凸棒石/g-C3N4复合材料的制备及其电催化析氧性能研究

以凹凸棒石(ATP)为载体, 通过原位沉积, 结合冷冻干燥、程序焙烧工艺在其表面负载不同质量分数的类石墨相氮化碳(g-C₃N₄)薄层材料, 制备系列ATP/g-C₃N₄复合材料用于电催化析氧反应, 产物标识为ATP/g-C₃N₄-w (质量分数w = mATP: (mATP + mg-C₃N₄)=0.33、0.40、0.50、0.67), 并研究在0.1 mol/L KOH的电解液中的电催化析氧性能。结果表明: g-C₃N₄薄层通过Si-O-C键牢固负载于凹凸棒石表面, 从而有效调变g-C₃N₄表面的电子层结构, 提供更多的催化活性位点。电催化析氧测试的结果表明: ATP/g-C₃N₄-0.50具有最优的析氧催化性能, 在10 mA/cm ²电流密度下其析氧过电位为410 mV, 塔菲尔斜率为118 mV/dec, 并表现出优异的析氧稳定性。     

钨基材料在电催化领域的应用进展

目前有关电催化剂应用的诸多研究领域,特别是商业领域,仍然由贵金属及其氧化物占据,但因其存在高成本和易中毒的壁垒而迫使科研人员把研究目光转向钨基电催化材料。氧化钨在制备条件得到有效控制的前提下可实现晶型结构及钨元素价态的多变,因此易于参加多种电化学反应,可实现对特定电化学反应的有效催化。回顾了不同晶相结构氧化钨基电极材料和不同异质结构钨基电极材料的制备方法、结构优势及其对各类电化学反应的优越催化性能,并从电极材料的制备和结构入手深入分析了文中所涉及电极材料优越催化性能的本质原因。以氧化钨及钨基电极材料的优越电催化性能为主线,辅以对电极材料的制备方法和特殊结构的分析,深入探讨了此类电催化材料的优势和发展方向,并总结本领域近5年的科研成果,为此类研究方向的深入开展提供了一定的借鉴经验。     

Co3O4/MoS2@TM异质结电极的制备及其析氧性能研究

电解水是一项有前景的大规模生产绿色氢能的技术。然而由于析氧反应(OER)的内在动力学缓慢,阻碍了这种能量转换技术的发展。这就需要高活性且稳定的电催化剂。因此本文采用简单的两步水热合成法在钛网上构筑了具有自支撑的异质结构Co_3O_4/MoS_2。所制备的Co_3O_4/MoS_2异质结催化剂在1 M KOH溶液中具有优异的OER催化性能,当电流密度达到10 mA·cm~(-2)时,所需过电势为306 mV,相应的塔菲尔(Tafel)斜率为51 mV dec~(-1)。催化剂表现出优异的OER催化活性源于异质结构以及Co_3O_4和MoS_2的协同作用。本工作为合理设计高效、低廉的复合型催化剂提供了有效的策略。     

金属氧化物电催化析氧机理的研究进展

电解水制氢是风能、潮汐能、太阳能等可再生能源转换和存储的重要途径。受限于四电子缓慢动力学过程,析氧反应（Oxygen evolution reaction, OER）是水分解的瓶颈反应。高活性析氧电催化剂是实现高效电解水制氢的关键之一。自从20世纪电解水发展以来,金属氧化物由于具有较好的活性和稳定性,是研究最深入也是最有发展前景的一类低成本析氧电催化剂。对催化反应机理的认识是高效析氧电催化剂理性设计的前提和关键,开发高效稳定的析氧催化剂并阐明其反应机理是目前析氧电催化领域的热点课题。按照一般异相催化的机理范式,人们提出了传统吸附机理,并建立了相应的活性预测模型来指导催化剂的研究。然而随着研究的深入,基于传统催化机理的活性预测模型和描述符的局限性日趋显现,部分新型催化剂的高活性和动力学特征无法用传统机理模型进行解释,析氧催化剂的研究也由此遭遇瓶颈。近年来,得益于各种先进表征手段和理论计算的飞速发展,新型析氧电催化机理逐渐被发展,为下一代高性能电催化剂的指明了方向。目前提出的新型催化机理主要有：晶格氧机理、双位点协同耦联机理、质子受体机理。同时,近期在一些催化剂中影响催化剂稳定性的阳离子析...     

Co2Ni1O4/不锈钢复合材料的制备及其电催化析氧性能

电解水包括析氢反应(HER)与析氧反应(OER),由于OER是复杂的4电子转移过程,制作出具有优异耐久性的高活性的非贵金属OER电催化剂对于电解水至关重要。为了降低成本,选择304型不锈钢网(SS)作为基体,使用电沉积的方法制备钴-镍双氢氧化物,利用真空煅烧的方法制备钴-镍氧化物。使用XRD、SEM、TEM、XPS和电化学工作站对Co₂Ni₁O₄/SS复合材料的晶体结构、形貌和电催化OER性能进行了研究。结果表明:电沉积制备的钴-镍双氢氧化物煅烧之后转变成尖晶石结构的钴-镍氧化物;在不锈钢表面成功合成了大量密集的层状结构;在1.0 mol/L KOH电解液中,Co₂Ni₁O₄/SS电极表现出优异的OER电催化性能,达到10 mA·cm?2电流密度时所需要的过电位仅为240 mV,Tafel斜率为53.92 mV·dec?1,并且表现出优异的稳定性。      

Revealing the Role of Electrocatalyst Crystal Structure on Oxygen Evolution Reaction with Nickel as an Example

Establishing a correlation between the crystal structure and electrocatalytic activity is crucial to the rational design of high performance electrocatalysts. In this work, taking the widely investigated nickel (Ni) based nonprecious oxygen evolution reaction (OER) catalyst as an example, for the first time, it is reported that the crystal structure plays a critical role in determining the OER performance. Similar‐sized nickel nanoparticles but in different hexagonal close‐packed phase and face‐centered cubic phase coated with N‐doped carbon shells, noted as hcp‐Ni@NC and fcc‐Ni@NC, are successfully prepared, respectively, in which the N‐coated carbon shell structures were also similar. Surprisingly, a dramatically enhanced OER performance of hcp‐Ni@NC in comparison with fcc‐Ni@NC is observed. The hcp‐Ni@NC only requires 305 mV overpotential to achieve the current density of 10 mA cm^?2, which is 55 mV lower than that of fcc‐Ni@NC, which can be ascribed to the influence of nickel crystal phase on the electron structure of N‐doped carbon shell. This finding will bring new thinking toward the rational design of high performance non‐noble metal electrocatalysts.     

Co@Co3O4@PPD Core@bishell Nanoparticle‐Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction

Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high‐performance primary zinc‐air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co₃O₄ core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co₃O₄@PPD core@bishell structure, obtained via a three‐step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co₃O₄ NPs encapsulated by ultrathin highly graphitized N‐doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N‐doped graphitic carbon outer shell and ultrathin nanocrystalline Co₃O₄ inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co₃O₄@PPD in air‐cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm^?2.     

Ultrathin Amorphous Nickel Doped Cobalt Phosphates with Highly Ordered Mesoporous Structures as Efficient Electrocatalyst for Oxygen Evolution Reaction

Herein, the facile preparation of ultrathin (≈3.8 nm in thickness) 2D cobalt phosphate (CoPi) nanoflakes through an oil‐phase method is reported. The obtained nanoflakes are composed of highly ordered mesoporous (≈3.74 nm in diameter) structure and exhibit an amorphous nature. Attractively, when doped with nickel, such 2D mesoporous Ni‐doped CoPi nanoflakes display decent electrocatalytic performances in terms of intrinsic activity, and low kinetic barrier toward the oxygen evolution reaction (OER). Particularly, the optimized 10 at% Ni‐doped CoPi nanoflakes (denoted as Ni10‐CoPi) deliver a low overpotential at 10 mA cm^?2 (320 mV), small Tafel slope (44.5 mV dec^?1), and high stability for OER in 1.0 m KOH solution, which is comparable to the state‐of‐the‐art RuO₂ tested in the same condition (overpotential: 327 mV at 10 mA cm^?2, Tafel slope: 73.7 mV dec^?1). The robust framework coupled with good OER performance enables the 2D mesoporous Ni10‐CoPi nanoflakes to be a promising material for energy conversion applications.     

Porous Hollow‐Structured LaNiO3 Stabilized N,S‐Codoped Graphene as an Active Electrocatalyst for Oxygen Reduction Reaction

A nanohybrid based on porous and hollow interior structured LaNiO₃ stabilized nitrogen and sulfur codoped graphene (LaNiO₃/N,S‐Gr) is successfully synthesized for the first time. Such a nanohybrid as an electrocatalyst shows high catalytic activity for oxygen reduction reaction (ORR) in O₂‐saturated 0.1 m KOH media. In addition, it demonstrates a comparable catalytic activity, longer working stability, and much better alcohol tolerance compared with commercial Pt/C behavior in same experiment condition. The obtained results are attributed to synergistic effects from the enhanced electrocatalytic active sites on the rich pore channels of porous hollow‐structured LaNiO₃ spheres and heteroatom doped efficiency on graphene structure. In addition, N,S‐Gr can meritoriously stabilize monodispersion of the LaNiO₃ spheres, and act as medium bridging for high electrical conductivity, thereby providing large active surface area for O₂ adsorption, accelerating reduction reaction, and improving electrochemical stability. Such a hybrid opens an interesting class of highly efficient non‐Pt catalysts for ORR in alkaline media.     

Formation of Ni–Fe Mixed Diselenide Nanocages as a Superior Oxygen Evolution Electrocatalyst

Exploring effective electrocatalysts is a crucial requirement for boosting the efficiency of water splitting to obtain clean fuels. Here, a self‐templating strategy is reported to synthesize Ni–Fe mixed diselenide cubic nanocages for the electrocatalytic oxygen evolution reaction (OER). The diselenide nanocages are derived from corresponding Prussian‐blue analog nanocages, which are first obtained by treating the nanocube precursor with a site‐selective ammonia etchant. The resulting Ni–Fe mixed diselenide nanocages perform as a superior OER electrocatalyst, which affords a current density of 10 mA cm^?2 at a small overpotential of 240 mV; a high current density, mass activity, and turnover frequency of 100 mA cm^?2, 1000 A g^?1, and 0.58 s^?1, respectively, at the overpotential of 270 mV; a Tafel slope as small as 24 mV dec^?1; and excellent stability in alkaline medium.     

Metal Atom-Doped Co3O4 Hierarchical Nanoplates for Electrocatalytic Oxygen Evolution

Electrocatalysts based on hierarchically structured and heteroatom-doped non-noble metal oxide materials are of great importance for efficient and low-cost electrochemical water splitting systems. Herein, the synthesis of a series of hierarchical hollow nanoplates (NPs) composed of ultrathin Co₃O₄ nanosheets doped with 13 different metal atoms is reported. The synthesis involves a cooperative etching−coordination−reorganization approach starting from zeolitic imidazolate framework-67 (ZIF-67) NPs. First, metal atom decorated ZIF-67 NPs with unique cross-channels are formed through a Lewis acid etching and metal species coordination process. Afterward, the composite NPs are converted to hollow Co₃O₄ hierarchical NPs composed of ultrathin nanosheets through a solvothermal reaction, during which the guest metal species is doped into the octahedral sites of Co₃O₄. Density functional theory calculations suggest that doping of small amount of Fe atoms near the surface of Co₃O₄ can greatly enhance the electrocatalytic activity toward the oxygen evolution reaction (OER). Benefiting from the structural and compositional advantages, the obtained Fe-doped Co₃O₄ hierarchical NPs manifest superior electrocatalytic performance for OER with an overpotential of 262 mV at 10 mA cm⁻², a Tafel slope of 43 mV dec⁻¹, and excellent stability even at a high current density of 100 mA cm⁻² for 50 h.     

The Flexibility of an Amorphous Cobalt Hydroxide Nanomaterial Promotes the Electrocatalysis of Oxygen Evolution Reaction

Structural flexibility can be a desirable trait of an operating catalyst because it adapts itself to a given catalytic process for enhanced activity. Here, amorphous cobalt hydroxide nanocages are demonstrated to be a promising electrocatalyst with an overpotential of 0.28 V at 10 mA cm^?2, far outperforming the crystalline counterparts and being in the top rank of the catalysts of their kind, under the condition of electrocatalytic oxygen evolution reaction. From the direct experimental in situ and ex situ results, this enhanced activity is attributed to its high structural flexibility in terms of 1) facile and holistic transformation into catalytic active phase; 2) hosting oxygen vacancies; and 3) structure self‐regulation in a real‐time process. Significantly, based on plausible catalytic mechanism and computational simulation results, it is disclosed how this structural flexibility facilitates the kinetics of oxygen evolution reaction. This work deepens the understanding of the structure–activity relationship of the Co‐based catalysts in electrochemical catalysis, and it inspires more applications that require flexible structures enabled by such amorphous nanomaterials.     

An Amorphous Nickel–Iron‐Based Electrocatalyst with Unusual Local Structures for Ultrafast Oxygen Evolution Reaction

Rationally designing active and durable catalysts for the oxygen evolution reaction (OER) is of primary importance in water splitting. Perovskite oxides (ABO₃) with versatile structures and multiple physicochemical properties have triggered considerable interest in the OER. The leaching of A site cations can create nanostructures and amorphous motifs on the perovskite matrix, thus facilitating the OER process. However, selectively dissolving A site cations and simultaneously obtaining more active amorphous motifs derived from the B site cations remains a great challenge. Herein, a top‐down strategy is proposed to transform bulk crystalline perovskite (LaNiO₃) into a nanostructured amorphous hydroxide by FeCl₃ post‐treatment, resulting in an extremely low overpotential of 189 mV at 10 mA cm^?2. The top‐down‐constructed amorphous catalyst with a large surface area has dual NiFe active sites, where high‐valence Ni³⁺‐based edge‐sharing octahedral frameworks are surrounded by interstitial distorted Fe octahedra and contribute to the superior OER performance. This top‐down strategy provides a valid way to design novel perovskite‐derived catalysts.